The effects of rapid rotation and bi-stability upon the density contrast between the equatorial and polar directions of a Be supergiant are re-investigated. Based on a new slow solution for different ...high rotational radiation-driven winds and the fact that bi-stability allows a change in the line-force parameters (α, k, and δ), the equatorial densities are about 102–104 times higher than the polar ones. These values are in qualitative agreement with the observations.
The theory of radiation-driven winds succeeded in describing terminal velocities and mass-loss rates of massive stars. However, for A-type supergiants the standard m-CAK solution predicts values of ...mass loss and terminal velocity higher than the observed values. Based on the existence of a slow wind solution in fast rotating massive stars, we explore numerically the parameter space of radiation-driven flows to search for new wind solutions in slowly rotating stars that could explain the origin of these discrepancies. We solve the one-dimensional hydrodynamical equation of rotating radiation-driven winds at different stellar latitudes and explore the influence of ionization changes throughout the wind in the velocity profile. We have found that for particular sets of stellar and line-force parameters, a new slow solution exists over the entire star when the rotational speed is slow or even zero. In the case of slow rotating A-type supergiant stars, the presence of this novel slow solution at all latitudes leads to mass losses and wind terminal velocities which are in agreement with the observed values. The theoretical wind-momentum-luminosity relationship derived with these slow solutions shows very good agreement with the empirical relationship. In addition, the ratio between the terminal and escape velocities, which provides a simple way to predict stellar wind energy and momentum input into the interstellar medium, is also properly traced.
Context. The formation and evolution of gas and dust environments around Be supergiants are still open issues. Aims. We intend to study the geometry, kinematics and physical structure of the ...circumstellar environment (CE) of the Be supergiant CPD−52 9243 to provide further insights into the underlying mechanism causing the Be phenomenon. Methods. The influence of the different physical mechanisms acting on the CE (radiation pressure, rotation, bi-stability or tidal forces) is somehow reflected in the shape and kinematic properties of the gas and dust regions (flaring, Keplerian, accretion or outflowing disks). To investigate these processes we mainly used quasi-simultaneous observations taken with high spatial resolution optical long-baseline interferometry (VLTI/MIDI), near-IR spectroscopy of CO bandhead features (Gemini/Phoenix and VLT/CRIRES) and optical spectra (CASLEO/REOSC). Results. High angular resolution interferometric measurements obtained with VLTI/MIDI provide strong support for the presence of a dusty disk(ring)-like structure around CPD−52 9243, with an upper limit for its inner edge of ~8 mas (~27.5 AU, considering a distance of 3.44 kpc to the star). The disk has an inclination angle with respect to the line of sight of 46 ± 7°. The study of CO first overtone bandhead evidences a disk structure in Keplerian rotation. The optical spectrum indicates a rapid outflow in the polar direction. Conclusions. The IR emission (CO and warm dust) indicates Keplerian rotation in a circumstellar disk while the optical line transitions of various species are consistent with a polar wind. Both structures appear simultaneously and provide further evidence for the proposed paradigms of the mass-loss in supergiant Be stars. The presence of a detached cold CO ring around CPD–52 9243 could be due to a truncation of the inner disk caused by a companion, located possibly interior to the disk rim, clearing the center of the system. More spectroscopic and interferometric data are necessary to determine a possible binary nature of the star.
Context. Be supergiants are evolved massive stars, enshrouded in a dense wind and surrounded by a molecular and dusty disk. The mechanisms that drive phases of enhanced mass loss and mass ejections, ...responsible for the shaping of the circumstellar material of these objects, are still unclear. Aims. We aim to improve our knowledge on the structure and dynamics of the circumstellar disk of the Large Magellanic Cloud Be supergiant LHA 120-S 73. Methods. High-resolution optical and near-infrared spectroscopic data were obtained over a period of 16 and 7 yr, respectively. The spectra cover the diagnostic emission lines from Ca ii and O i, as well as the CO bands. These features trace the disk at different distances from the star. We analyzed the kinematics of the individual emission regions by modeling their emission profiles. A low-resolution mid-infrared spectrum was obtained as well, which provides information on the composition of the dusty disk. Results. All diagnostic emission features display double-peaked line profiles, which we interpret as due to Keplerian rotation. We find that the profile of each forbidden line contains contributions from two spatially clearly distinct rings. In total, we find that LHA 120-S 73 is surrounded by at least four individual rings of material with alternating densities (or by a disk with strongly non-monotonic radial density distribution). Moreover, we find that the molecular ring must have gaps or at least strong density inhomogeneities, or in other words, a clumpy structure. The optical spectra additionally display a broad emission feature at 6160–6180 Å, which we interpret as molecular emission from TiO. The mid-infrared spectrum displays features of oxygen- and carbon-rich grain species, which indicates a long-lived, stable dusty disk. We cannot confirm the previously reported high value for the stellar rotation velocity. He i λ 5876 is the only clearly detectable pure atmospheric absorption line in our data. Its line profile is strongly variable in both width and shape and resembles of those seen in non-radially pulsating stars. A proper determination of the real underlying stellar rotation velocity is hence not possible. Conclusions. The existence of multiple stable and clumpy rings of alternating density recalls ring structures around planets. Although there is currently insufficient observational evidence, it is tempting to propose a scenario with one (or more) minor bodies or planets revolving around LHA 120-S 73 and stabilizing the ring system, in analogy to the shepherd moons in planetary systems.
Objectives
Behcet’s disease (BD) is a systemic vasculitis characterized by cardiovascular complications. Early diagnosis of these complications can reduce morbidity and mortality. Carotid artery ...intima–media thickness (cIMT) and the logarithmic value of triglyceride to high density lipoprotein ratio (atherogenic index of plasma, AIP) are good markers of atherosclerosis. The purpose of this study was to investigate whether AIP is a predictive marker of subclinical atherosclerosis in BD patients.
Patients and methods
A total of 84 BD patients (60 male, 24 female) and 84 healthy control individuals (58 male, 26 female) were included in this study. cIMT measurements were made, and AIP values were calculated.
Results
cIMT (
p
< 0.001) and AIP (
p
< 0.001) values of the BD patients were higher than those of the control group. A strong independent relationship was found between the AIP value and cIMT (β = 0.232,
p
= 0.018). In the subgroup analysis, the cIMT and AIP values of male BD patients were higher than those of female BD patients.
Conclusion
Increased AIP and cIMT values can be a good marker for subclinical atherosclerosis in BD patients, especially in male BD patients.
Do hummingbirds see in ultraviolet? Curé, M; Palacios, A G
The open medical informatics journal,
04/2009, Volume:
3, Issue:
1
Journal Article
Peer reviewed
Open access
We present a numerical model to fit the electroretinogram (ERG), a gross evoked eye visual potential, that originate in the retina through photons absorption by photoreceptors and then involve the ...contribution form others retinal neurons. We use the ERG measured in a hummingbird, to evaluate the most likely retinal mechanism - cones visual pigments and oil-droplets - that participate in their high dimensional tetra or pentachromatic color hyperspace. The model - a nonlinear fit - appears to be a very useful tool to predict the underlying contribution visual mechanism for a variety of retinal preparation.
To establish serum YKL-40 concentrations in patients with endometriosis compared to age-matched healthy subjects.
This was a cross-sectional clinical study conducted in a tertiary care center. ...Demographics and serum YKL levels were determined and noted in a total of 63 cases (33 endometriosis patients, 30 healthy controls). Measurement of YKL-40 levels was made using a YKL-40 enzyme-linked immunosorbent assay (ELISA) kit according to the manufacturer's protocol.
The mean serum YKL-40 levels of the patient group was 106.0 +/- 15.9 (range 23.44 to 382.55) years, while the mean serum YKL-40 levels of the controls was 52.2 +/- 7.0 (range 22.35 to 160.0) years (p = 0.003).
This is the first study evaluating serum YKL-40 levels in endometriosis. The present results indicate that YKL-40 levels were increased in patients with endometriosis compared to controls. The authors propose that circulating YKL-40 levels could be a novel biomarker for diagnosis and follow-up of endometriosis.
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